This study investigated trajectories of ethnic discrimination experiences in school, diversity climates as contextual antecedents, and school adjustment as outcome. Latent-Growth-Mixture-Models of repeated self-reported discrimination over 3 years (2012-2015) by 1445 ethnically-minoritized adolescents of Turkish and Moroccan background in 70 Belgian schools (52.6% boys, M[subscript age] = 15.07) revealed four trajectories: low (72.5%), moderate (16.6%), initially-high (6.5%), or increasingly high discrimination (4.4%). Adolescents who attended schools with more minoritized peers, or schools that valued cultural diversity and equality, were more often in low-discrimination trajectories, which predicted better academic outcomes. Overall, school diversity climates can protect minoritized adolescents from experiencing persistent or initially high discrimination over time. Moreover, high discrimination at any point in schooling--initially or later--is harmful to adolescents' school adjustment.